Term used on GEnie, Usenet and other electronic fora to describe the
tendency of a {thread} to drift away from the original subject of
discussion (and thus, from the Subject header of the originating
message), or the results of that tendency. The header in each post
can be changed to keep current with the posts, but usually isn't due
to forgetfulness or laziness. A single post may often result in
several posts each responding to a different point in the original.
Some subthreads will actually be in response to some off-the-cuff
side comment, possibly degenerating into a {flame war}, or just as
often evolving into a separate discussion. Hence, discussions aren't
really so much threads as they are trees. Except that they don't
really have leaves, or multiple branching roots; usually some lines
of discussion will just sort of die off after everyone gets tired of
them. This could take anywhere from hours to weeks, or even longer.
The term `topic drift' is often used in gentle reminders that the
discussion has strayed off any useful track. "I think we started with
a question about Niven's last book, but we've ended up discussing the
sexual habits of the common marmoset. Now that's topic drift!"
[glossary]